This invention relates to barrel locks, specifically to means for preventing rotation of a barrel lock when opened by a key.
Barrel locks are used to secure meter rings like the ones shown in U.S. Pat. No. 4,702,093 (DeWalch, 1987), as well as a variety of other locking hardware. In the present disclosure, the term “locking hardware” is used to refer to any device which is secured by a barrel lock. A barrel lock, as defined in the present disclosure, is commonly characterized as having a generally cylindrical case with a head portion, a smaller diameter shank portion, and a shoulder portion interposed between the head and shank portions. The shank portion includes retaining means, usually a pair of retractable steel balls, to prevent extraction of the lock from the meter ring or other locking hardware when the lock is locked. Usually barrel locks are removed from the locking hardware when they are unlocked. In many cases removal of the lock is required for opening the locking hardware.
Many barrel locks, such as the one described in U.S. Pat. No. 4,289,000 (Nielsen, 1981), rely on axial movement of the key to actuate the lock. Although the operation of axially actuated locks is independent of lock rotation, these locks have a relatively small number of possible key codes, are often easy to pick, and require the use of a rather large and cumbersome key. To overcome these difficulties, barrel locks have been developed which are actuated by rotation of the key relative to the lock. In the present disclosure, this type of lock will be referred to as a “rotationally actuated barrel lock.”
The generally cylindrical shape of most barrel locks allows them to rotate freely within the locking hardware. Although rotationally actuated barrel locks have many advantages, their rotation within the locking hardware can potentially cause a problem during lock actuation. Whenever the torque required to unlock the lock is greater than the torque required to rotate the lock within the locking hardware, the entire lock will rotate with the key. Since no relative rotation occurs between the lock and the key, the lock remains locked. In this situation, the user is clearly in need of some means to induce the relative rotation of the lock and key.